Oal

[LoneWolf]

I don't know if this has been discussed before but I couldn't find anything. When the OAL is listed in the loading manuals I didn't really see a general explanation for it. I'm assuming it is for three reasons : so the powder isn't compressed, so the round will work in the magazine and so it will fit in the barrel ? Based on this if the round fits in the barrel and magazine the OAL will be OK ? I haven't been able to find a load with all the components that I am using.

I recieved my 550B yesterday and I'm assembling today ! Thanks !!

[old shooter]

Lonewolf,

You have the right idea about the 3 reasons, but make sure reason 1 is in your lineup. Bullet seating depth has a great deal to do with pressure. Some loads will tolerate compression if the loading manual states so, however I have always been reluctant to do this on my own. If you go with good resources for your load data, you should be in good shape.

BTW, what cal. are you loading?

[LoneWolf]

Hi old shooter ! I just finished setting up my 550 . I'm set up for 9MM. I'm using Rainier 124 gr RN bullets, Starline brass, Titegroup powder and Federal SP primers. I set all the dies (and wasted about 8 cases) but so far it's looking good. I'm checking a few powderless/primerless rounds now and this is what I have : OAL 1.155 , crimp = .375 (.355 bullet +.011+.011(case walls) - .002 = .375), the belling appears to be perfect as well as the crimp. I was thinking of starting with a 4.0 gr load. The two manuals I have don't have the same components but seem to agree (for bullet weight) 3.8 min. and 4.2 max of Tightgroup. What do you guys think of this set up so far ?

I also built a portable press bench two days ago which is working great - cost was $12.80 . I had the B&D workmate in the garage. I brought it in the basement and bought a broken kitchen countertop for $10.00. I opened the top to max and made a template of the holes (on the workmate). I transfered the template and drilled the countertop and bolted ($2.80) it to the workmate. If I knew how to post a picture I would.

Thanks , Doug

[rhyrlik]

COAL is a reflection of the cartrige's internal airspace. The less airspace, the higher the pressure will be. The 9mm is very sensitive to internal changes of airspace. I read a study where it was established that with a certain powder, a .010" reduction in COAL resulted in a 10000PSI increase in pressure. This should scare even the most experienced reloader.

I would therefore start at 3.0 grains and load five rounds in .2 grain increments. If the fifth round is mild, then load five and start from there. This is the safest way to do it because you don't have any data using your particular components.

[ErikW]

1.155" is long for 9mm. It's perfect for a Tanfoglio, but could cause trouble in other magazines. You might want to load up a magazine full of primerless/powderless dummies and load your (SIG?) magazines to see whether that OAL will fit in them.

Another reason to stay at the book-specified OAL is you could get the bullet dangerously close to the rifling and radically increase pressure.

[TRG65]

I determine my OAL by the magazine and the leade on the gun . For instance, in my G-34 I load to 1.158 because at 1.163-1.164 the mag starts being tied up. In my Springfield 9mm, I run an oal of 1.180. The magazines start binding at around 1.185-1.187. However when loading long like this you must make sure that your bullets are not being driven into the rifliing, because of the pressure increase that Eric mentioned. Neither of these loads touch the rifling IN THESE GUNS, so I'm as close as I can be but not touching.

[LoneWolf]

In all the reading I've been doing the past few weeks nowhere have I found (as mentioned in my first post) a reason for the OAL - I was just theorizing. Also I couldn't find any method ( in print or on various sites) of setting my OAL to my pistol - Erik was right it's a Sig P228. How would I know if the bullet is being driven into the rifling ? Is there a way to see this in my barrel without actually firing it ? Thank you all !

[Flexmoney]

Make some extra long dummy rounds...pre-measured.

"Paint" the bullet portion (Sharpie marker should work).

Feed the dummy rounds one at a time. Do so until you find the length that shows the bullet is touching the rifling (rub marks).

Back it off.

I often think that OAL should be as long as possible. Usually, that means less case pressure...and, a smaller distance the bullet has to "jump" before it engages the rifling.

But, the feeding reliability is a big part of determining OAL.

[TRG65]

I've tried the method that Flex suggests w/ a sharpie and it must work for some people but it sure hasn't ever for me. I make some dummy rounds a little longer than I want to load and put a very very light crimp on them. then I set them in the chamber and let the slide down with full force (Yes I know this is bad for the extractor). Then I pull the slide back slowly and if I feel any extra restistance then I know its too long and repeat the procedure a little shorter. If I felt resistance, I then remeasure the oal and if it is shorter than it was when it went in my next starting point is a little shorter than the remeasure.

This is essentially the same procedure that is used with rifles, except the trial and error is eliminated with rifles by "gagues" like the stony point chamber-all.

[ErikW]

I think some factory barrels might be liability-proofed with long throats. They certainly do that with rifles. With a 9mm SIG, you'll probably reach the maximum magazine-compatible length before you hit the rifling. Send a PM to forum member David Olhasso (Production GM with a SIG); he might be able to suggest a good OAL for you.

[Nik Habicht]

And odds are that it will be around 1.110....

[LoneWolf]

You guys are the best !! I think I'll try Flexmoney's idea over the weekend and see how it works out. I'll also try to contact Rainier and Hodgdon and see what they say. Then I'll compare my results (Flexmoney's method) against what they recommend. As soon as I get the info and my results I'll post them here. Thanks again !

[Flexmoney]

My method might not be the best...and, I usually use candle soot over the sharpie for gun stuff.

I think you will get it figured out though.

[TBF]

rhyrlik,

Not to make things more comlpicated, but not all bullets are the same and OAL will vary depending on nose shape. ( JHP, flatpoint, roundnose etc )

My SOP is :

1: load dummy rounds as long as mag will allow.

2: See if it's too long for the gun. ( do they feed ? Do they hit the rifling ? )

3: load a few rounds at 10% under max or minimum start load, and see if they feed while actually firing.

4: Adjust OAL as required, then work load up to desired pressure/velocity.

Good advice above.

About .020 off the front of mag is where I usually start playing around with dummy rounds. Make sure they move up and down in mag freely.

The OAL in the manual usually refers to MIN. OAL for bullets tested.

Longer is always safe provided it's not jamming the bullet into the rifling. ( and IME that does not happen very often )

Good luck.

Travis F.

[D.Hayden]

I was thinking of starting with a 4.0 gr load. The two manuals I have don't have the same components but seem to agree (for bullet weight) 3.8 min. and 4.2 max of Tightgroup. What do you guys think of this set up so far ?

It's not apples/apples but close. I'm shooting a 124 Zero with TiteGroup and get these:

3.8 = Avg 1006fps = 124.7PF

4.0 = Avg 1066fps = 132.1pf

4.2 = Avg 1087fps = 134.8pf

So I ned at least the 4.0 (maybe 3.9, but with less cushion) to get the minimum 125pf for USPSA

Make sure you chron your loads

My OAL = 1.15

[eric nielsen]

If you change bullet shapes, your goal is to have the bullet strike the feedramp with the same amount of forward slide travel, assuming your old bullet style was running well thru the gun.

If you SLOOOOWLY hand-cycle the gun and the slide just sort of hangs up for a moment, then goes forward with a tap, most likely your rounds are too long for that magazine. Again, this is assuming your mag is set up right: the feedlips are the right length and the correct gap distance.

I'll probably make someone mad, but I'll rank the quality of wide-body mags, bought brand new. Not a single-stack expert, but McCormick is good.

#1 SV

#2 Glock factory

#3 STI (feedlip length sometimes too much, gap sometimes wrong)

#4 Very old Caspian, TZ and Para (made before 1995 is usually fine)

#5 Newer "pre-ban" mags for Caspian and Para (lots of problems)

#6 "Pre-ban" mags for Smith, Sig, TZ, etc (lots of problems)

[LoneWolf]

Well I used Flexmoney's method and when I saw marks I backed off the OAL. I came up with 1.10" for my OAL , .376 for my crimp and 3.8 grains of Tightgroup. I went to the range this morning and they worked flawlessly! They were very soft in recoil yet cycled well and the slide stayed open on the last round. The only problem is my Sig won't adjust for elevation and the shots grouped about 6" low. I guess I'll have to "slowly" work up the powder charge. Thanks

[Flexmoney]

1.100 sounds short.

Max book length seem to be just under 1.170.

It seems weird to me that yuor SIG would hit the rifling at 1.100?

Short rounds can cause pressure.

[ErikW]

Ditto.

The Viht. manual lists some short OALs for ultra-light bullets, but 1.10" for a 124 RN seems too short.

[Flexmoney]

I measured, at one point, some Winchester white-box, 115 FMJ's. If I recall, they measured 1.160.

[LoneWolf]

I probably (most likely) backed off too much trying to be cautious ! Once I saw the marks I backed off and figured I'd play it safe. I will measure the last round that touched the riflings and how much would you suggest backing off ?

[D.Hayden]

I've seen posts (Brian's or Matt's books maybe), about 9MM being way sensitive to short OALs, with huge increases in pressure. I would think 1.15+ would be more typical.

[rookie mode on] it seems that the longer you can use the beter for this petite case

[Flexmoney]

Try a Winchester white box (Walmart Val-u-pak).

Any 9mm ought to be able to eat those with the bullet hitting the rifling.

You aren't being safe by going shorter. As said...that is causing more pressure.

[TRG65]

If I have a pistol round that is touching I would only back off about 0.005" This should allow for some natural play in your during loading and still keep all the rounds off the lands. The shortest I have had to load a RN was 1.150. That was a .357 147 gr RN in a regular .355 barrel. Before that I loaded 115 RNs and those were loaded to about 1.160 because that is what my Glock mags would allow. I have shot 124 FP's in a brand new Bar-Sto, those had to be loaded very short not to touch, like 1.08." My wife's Sig with a factory barrel has never had a problem with long loaded rounds. I would guess you should easily be able to load 1.150-1.160 with out a problem.

With the sharpie or smoking method, be carefull in what you think is rifling contact. Semi's will cause the nose of the bullet to scrape along the side of the chamber during extraction, because of the extractor tension. That has messed me up several times.

If this is useless information, then totally disregard.

[LoneWolf]

The method I am using is placing the cartridge (w/sharpie) in the barrel by hand - barrel removed from slide. So after finding the length which the bullet isn't being marked reduce .005 and then check it in the magazine - does this sound right ?